• Measurable, i.e., a criterion that allows its quantified measurement upon some
evaluation scale;
• Ordinal, i.e., a criterion that defines an ordered set of acceptable values that
allow its evaluation using a qualitative or a descriptive scale;
• Probabilistic, i.e., a criterion that uses probability distributions to represent uncertainty in its evaluation;
• Fuzzy, i.e., a criterion whose evaluation is represented in relation to its possibility to belong in one of the intervals of a qualitative or descriptive evaluation
scale.
From a broad perspective, a family of criteria can be used to facilitate the representation of user preferences in recommender systems as well. Therefore, we can